Maintain peers across all custody column subnets #7865
Description
When a node is not able to connect to supernodes, it sometimes struggle to maintain peers across all 128 data column subnets.
This means node won't be able to sync or keep up with head if it's not able to retrieve it's custody columns.
Similar to maintain_sync_committee_peers, we should try to maintain peers across all subnets, to ensure we can retrieve / publish data correctly.
There's also separate issue to bump peer count if necessary: #6920